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Brightest Lights

StarDate:

January 21, 2012

The two brightest stars in the night sky stairstep up the southern sky late tonight. To see the lower of the two, you need to be south of about Phoenix or Birmingham. But the other shines high enough to see from the entire country.

That one is Sirius, the brighter of the two, which stands well up in the south in late evening. It’s the leading light of Canis Major, the big dog, so it’s also known as the Dog Star.

The other star is Canopus, in Carina, the keel. Around 11 or 12 o’clock, look for it below Sirius and a little to the right — but only from southern latitudes. Canopus is so far south, in fact, that it never pops above the horizon from Denver, Baltimore, or points northward.

In fact, skywatchers at far-northern latitudes get to see less of the heavens than those who are closer to the equator. The great dome of the night sky is split into two hemispheres. The dividing line is the celestial equator, which is the projection of Earth’s equator into space.

People on the equator get to see both hemispheres. But as you move away from the equator, you lose a greater and greater slice of the universe, because more of the sky is blocked from view by Earth itself. The size of the slice is equal to your latitude. If you live at 40 degrees north, for example — roughly the latitude of Salt Lake City — you lose the southernmost 40 degrees of the sky. Canopus is in that region of the sky — just below the horizon and out of sight.

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